Separator for organic electrolyte battery, process for producing the same and organic electrolyte battery including the separator

ABSTRACT

An organic electrolyte battery separator is composed of a nonwoven comprising a heat-and-humidity gelling resin capable of gelling by heating in the presence of moisture and another fiber. The other fiber is fixed with a gel material obtained by causing the heat-and-humidity gelling resin to gel under heat and humidity. The nonwoven has a mean flow pore diameter of 0.3 μm to 5 μm and a bubble point pore diameter of 3 μm to 20 μm as measured in accordance with ASTM F 316 86. Thereby, the other fiber constituting the nonwoven can be fixed with the heat-and-humidity gelling resin, thereby making it possible to obtain a desired mean flow pore diameter and bubble point pore diameter. As a result, an organic electrolyte battery having a high level of safety, less occurrence of a short circuit, high battery characteristics is provided.

TECHNICAL FIELD

The present invention relates to a battery separator made of a nonwoventhat can be used in an organic electrolyte battery, particularlypreferably in a lithium ion secondary battery. The present inventionalso relates to an organic electrolyte battery comprising the batteryseparator.

BACKGROUND ART

Recent advances in IT (information technology) and environmental issueshave spurred the development of secondary batteries, such as, forexample, an alkaline secondary battery and an organic electrolytesecondary battery. Particularly, a lithium ion secondary batteryemploying an organic electrolyte, which has high voltage, high capacityand high power, and in addition, light weight, has had an impact on themarket, which demands small-size and light-weight products. Further,this battery has been developed for hybrid electric vehicles (HEV) andpure electric vehicles (PEV). This lithium ion secondary batterycomprises a positive electrode made of a composite metal oxide materialthat can absorb/store and release lithium ions, a negative electrodemade of a carbon material or the like that can absorb/store and releaselithium ions, a separator, and an organic electrolyte. Particularly, inthis lithium ion secondary battery, an electrode that is made byelectrochemically alloying lithium with another metal in the presence ofan electrolyte may be used in order to improve battery performance.However, this alloy electrode has a problem in that fine powder oflithium alloy is generated in the alloying process and the alloy powderpenetrates through the separator and reaches the other electrode,resulting in a short circuit (hereinafter referred to as a fine powdershort). There is particularly a demand for a separator with a small porediameter to prevent fine powder short circuits. On the other hand,repeated charging and discharging of a battery causes needle-likeformation of the fine powder, which grows on the electrode and finallypenetrates through the separator, resulting in a short circuit(hereinafter referred to as a dendritic short circuit). Therefore, theseparator requires a sheet having a high level of resistance to piercing(hereinafter referred to as puncture strength).

Further, the number of electrodes or the overall electrode area per thevolume of a battery is one of the factors that determine the lifetime ofa secondary battery. The battery life may be prolonged by decreasing thethickness of the electrode as well as the thickness of the separator toincrease the number of electrodes or the overall electrode area.Therefore, there is a demand for a thin separator.

At the present time, a fine-porous film is used, which satisfies all ofthe above-described conditions. However, the production process of thefine-porous film is complicated and expensive. Therefore, nonwovens,which are inexpensive and satisfy the puncture strength and thicknessrequirements, have been studied in place of the fine-porous film.

Various nonwovens for use in an organic electrolyte battery separatorhave been studied. For example, Patent Publications 1 and 2 listed belowpropose nonwovens with a small pore diameter, which are prepared by ameltblown method. Particularly, Patent Publication 1 proposes a nonwovenwith a bubble point pore diameter of 30 μm or less, specifically anonwoven with a bubble point pore diameter of 25 μm or less, which is acomposite nonwoven of polypropylene and polyethylene prepared by themeltblown method.

Besides the meltblown method, for example, Patent Publication 3 listedbelow proposes a wetlaid nonwoven with a bubble point pore diameter of 9μm, which is made of small fineness polyethylene terephthalate fiber.Further, as an organic electrolyte battery separator made of a wetlaidnonwoven containing a splittable composite fiber, for example, PatentPublication 4 listed below proposes a nonaqueous electrolyte batteryseparator that is prepared by mixing a splittable composite fibercontaining an ethylene-vinyl alcohol copolymer as at least one componentwith a hot melt fiber, splitting the splittable composite fiber andattaching polyalkylene denatured polysiloxane to the resultant wetlaidnonwoven via a chemical bond. Patent Publication 5 listed below proposesa nonaqueous electrolytic solution battery separator that is made of awetlaid nonwoven that mainly contains a plate-like ultrafine fiberprepared by dividing a splittable composite fiber.

Patent Publications 6 to 9 propose separators made of a nonwoven that isprepared by bonding an ethylene-vinyl alcohol copolymer under heat andhumidity.

-   -   Patent Publication 1: JP H7-138866A (claim 2)    -   Patent Publication 2: JP 2000-123815A    -   Patent Publication 3: JP 2002-151037A (page 6, examples 1 and 2)    -   Patent Publication 4: JP 2000-285895A    -   Patent Publication 5: JP 2001-283821A    -   Patent Publication 6: JP H3-257755A    -   Patent Publication 7: JP S63-235558A    -   Patent Publication 8: JP H5-109397A    -   Patent Publication 9: JP H8-138645A

However, the above-described battery separators have the followingproblems: Firstly, the meltblown nonwoven disclosed in PatentPublication 1 is formed of a polyolefin fiber that is not drawn in theprocess, so that its single fiber strength is low. Therefore, thisnonwoven is prone to be torn during assembly of a battery, and ifassembled, its low puncture strength leads to a low level of capabilityof preventing the dendritic short circuit. In Patent Publication 2, itis attempted to improve the strength of the nonwoven by usingpolyphenylene sulfide to suppress the occurrence of defects duringassembly of a battery. However, polyphenylene sulfide is expensive, i.e.it does not contribute to cost-cutting. The separator of PatentPublication 3 has a bubble point pore diameter of 9 μm and has a certainlevel of fine powder short circuit preventing capability, however, itsmean flow pore diameter is not discussed therein and is notsatisfactory. When component fibers are bonded together with heat toform a nonwoven, the process needs to be performed at a temperature thatis equal to or higher than about the melting point of a binder resin. Atsuch a temperature, however, thermal shrinkage occurs in associationwith heat melting of the binder fiber. As a result, the nonwovenundergoes thermal shrinkage, resulting in a decrease in yield ofproduction of the nonwoven (hereinafter simply referred to as a“yield”). Specifically, variations in mass per unit area, or weight perunit area, thickness or the like, or irregular pore diameters are likelyto occur in the nonwoven. Therefore, the electrolytic solution cannot bekept uniform, or both a fine powder short circuit and a dendritic shortcircuit are likely to occur, resulting in a high defect rate of abattery (hereinafter also referred to as a “battery defect rate”). Whenpressure bonding using a thermal roller or the like is performed inorder to decrease the pore diameter and thickness of a nonwoven,significant fusion bonding occurs on a surface of the nonwoven (densesurface) and less inside the nonwoven (coarse inside), leading to anincrease in the battery defect rate. Further, the electrolytic solutionis not kept uniform, so that an internal resistance of the battery isincreased. In the separator of Patent Publication 4, a wetlaid nonwovenhaving a low mass per unit area of 12 to 14 g/m² and a predeterminedthickness, which contains a splittable composite fiber, is produced, andthereafter, the wetlaid nonwoven is immersed in an aqueous solution ofpolyalkylene denatured polysiloxane, thereby attempting to decrease themicropore diameter of the nonwoven. However, for such a low-mass perunit area nonwoven, it is difficult to produce a nonwoven having auniform mean flow pore diameter and bubble point pore diameter. In fact,the nonwoven has a large variation in pore diameter, leading to instablepuncture strength. Further, a splittable composite fiber containing anethylene-vinyl alcohol copolymer as at least one component is mixed witha hot melt fiber to obtain a wetlaid nonwoven, which is in turnsubjected to a dry heat calender process at a processing temperaturethat causes the hot melt fiber to exhibit its adhesion ability.Therefore, only the hot melt fiber contributes to adhesion ability, sothat the puncture strength is insufficient. In the separator of PatentPublication 5, a splittable composite fiber made of two components,i.e., polypropylene/polyester, nylon 66/polyester, andpolypropylene/polyethylene, is split into plate-like microfine fibers,which are in turn subjected only to a heat calender process at atemperature that is below the melting point of the lower-melting pointcomponent. Therefore, it is difficult to obtain a nonwoven having auniform mean flow pore diameter and bubble point pore diameter,resulting in a nonwoven having a significant variation in pore diameter.Therefore, no stable puncture strength is acquired. Although PatentPublications 6 to 9 disclose separators containing fibers that arebonded under heat and humidity, all the separators are intended to beused for an alkaline battery. It is difficult to obtain a separatorhaving a small pore diameter that is required for an organic electrolytebattery.

DISCLOSURE OF INVENTION

The present invention is provided to solve the above-described problems.An object of the present invention is to provide an organic electrolytebattery separator made of a nonwoven that can be produced inexpensively,has an excellent yield in production, has an excellent level ofelectrolytic solution holding ability, and can prevent a fine powdershort circuit and a dendritic short circuit when incorporated into abattery (i.e., a low battery defect rate), in place of nonwovens thatconventionally have been proposed as organic electrolyte batteryseparators. Another object of the present invention is to provide anorganic electrolyte battery that has an excellent level of safety, has ashort circuit less often, and has excellent battery characteristics.

The organic electrolyte battery separator of the present invention ismade of a nonwoven containing a resin that can gel by heating in thepresence of moisture (hereinafter referred to as a “heat-and-humiditygelling resin”) and another fiber. The other fiber is fixed by theheat-and-humidity gelling resin that gels under heat and humidity toform a gel material (hereinafter referred to as a “gel material”). Thenonwoven has a mean flow pore diameter of 0.3 μm to 5 μm and a bubblepoint pore diameter of 3 μm to 20 μm as measured in accordance with ASTMF 316 86.

The organic electrolyte battery separator of the present invention canbe produced using the following method. Specifically, a method forproducing an organic electrolyte battery separator comprising aheat-and-humidity gelling fiber in which a resin capable of gelling byheating in the presence of moisture (hereinafter referred to as a“heat-and-humidity gelling resin”) is present on at least a portion of asurface of the fiber, and another fiber, has at least the followingsteps:

A. preparing a nonwoven sheet comprising a heat-and-humidity gellingfiber and another fiber;

B. subjecting the nonwoven sheet to a hydrophilic treatment;

C. providing moisture to the hydrophilic-treated nonwoven sheet(hereinafter referred to as a “hydrophilic nonwoven sheet”) to obtain awater-containing sheet; and

D. subjecting the water-containing sheet to a heat-and-humiditytreatment (hereinafter referred to as a “gel processing”) using a heattreatment device that is set to a certain temperature within a range ofno less than a temperature at which the heat-and-humidity gelling resingels and no more than “the melting point of the heat-and-humiditygelling resin −20° C.”, to cause the heat-and-humidity gelling resin togel, and fixing the other fiber using the heat-and-humidity gellingresin gel.

An organic electrolyte battery of the present invention is obtained byincorporating the separator.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross-sectional view showing a method of measuring a contactangle on a surface of a nonwoven used in an example of the presentinvention.

FIG. 2 is a 200×SEM micrograph of a surface of a nonwoven sheet obtainedin Example 1 of the present invention.

FIGS. 3A to 3D are 200×SEM micrographs of a surface of a batteryseparator obtained in Example 1 of the present invention.

FIG. 4 is a 500×SEM micrograph of a section of the battery separatorobtained in Example 1 of the present invention.

FIGS. 5A and 5B are 300×SEM micrographs of a surface of a nonwoven sheetobtained in Example 5 of the present invention. FIGS. 5C and 5D are 300×cross-sectional photographs of a surface of the nonwoven sheet obtainedin Example 5 of the present invention.

FIGS. 6A and 6B are 300×SEM micrographs of a surface of a batteryseparator obtained in Example 5 of the present invention. FIGS. 6C and6D are 1000× cross-sectional photographs of a surface of the batteryseparator obtained in Example 5 of the present invention.

1: glass plate, 2: sample, 3: pure water

BEST MODE FOR CARRYING OUT THE INVENTION

The present inventors have diligently researched to conceive that aseparator made of a nonwoven that excellently resists a fine powdershort circuit can be obtained by establishing an appropriate mean flowpore diameter range and bubble point pore diameter range, but notsufficiently by only decreasing a pore diameter. It was found that thiscan be achieved by reducing shrinkage of a nonwoven when subjected to athermal treatment to obtain a micropore diameter and fixing a binderresin in a thickness direction of the nonwoven substantially uniformly.To obtain such a nonwoven, a heat-and-humidity gelling resin is causedto gel using a particular thermal processing method to fix otherfiber(s). Thereby, the mass per unit area and thickness irregularity arereduced. Further, the puncture strength is large, and a variation in thepuncture strength is suppressed. Therefore, the yield of production ofthe separator is excellent, and the battery defect rate is low.Particularly, the dendritic short circuit prevention ability is alsoexcellent. Furthermore, it is found that the separator is less expensivethan conventional fine-porous films. Hereinafter, the organicelectrolyte battery separator of the present invention will be describedin detail.

To obtain a nonwoven with a small pore diameter, a method of pressingand spreading a resin that has been softened or melted by heating, usinga means for thermally bonding with a predetermined pressure or more,such as thermal rolling or the like, to fill a gap between fibers, maybe used. However, conventional heat-melting resins need to be heated tothe melting point of the heat-melting resin or more. In this case, adimension of the nonwoven is significantly changed due to thermalshrinkage associated with the melting of the heat-melting resin. As aresult, the yield is reduced, or variations in the mass per unit area,the thickness, the pore diameter, the puncture strength or the like areincreased, so that the battery defect rate, particularly the shortcircuit prevention ability, is low. When a thermal roller or the like isused, fusion bonding is likely to occur significantly on a surface of anonwoven (dense surface) and less inside the nonwoven (coarse inside).Therefore, it is difficult for the electrolytic solution holding abilityto be uniform, likely leading to an increase in the battery defect rate.

Therefore, in the present invention, a heat-and-humidity gelling resinthat becomes a gel and swells in the presence of moisture is used inplace of conventional heat-melting resins, and another fiberconstituting a nonwoven is fixed using a gel material that is obtainedby gelation of the heat-and-humidity gelling resin under heat andhumidity so that an appropriate mean flow pore diameter range and bubblepoint pore diameter range are obtained. By fixing the other fiberconstituting the nonwoven using the gel material, a puncture strength ofthe separator is increased, thereby resisting tearing during assembly ofa battery and obtaining an excellent level of dendritic short circuitprevention ability. Further, the fine powder short circuit preventionability is caused to be excellent by establishing an appropriate meanflow pore diameter range and bubble point pore diameter range. As usedherein, the gel material indicates a resin (solid material) that issolidified after gelation of the heat-and-humidity gelling resin underheat and humidity. In the organic electrolyte battery separator of thepresent invention, the other fiber constituting the separator is fixedusing the gel material.

Further, when the organic electrolyte battery separator of the presentinvention is produced, by uniformly dispersing the heat-and-humiditygelling resin into the nonwoven sheet, it is made more likely to obtainan appropriate mean flow pore diameter range and bubble point porediameter range. Furthermore, by causing the nonwoven sheet to holdmoisture uniformly before gel processing, it is made possible to causethe heat-and-humidity gelling resin provided in the nonwoven sheet togel substantially uniformly, whereby the component fibers can be fixedmore uniformly using the gel material. Therefore, it is made more likelyto obtain an appropriate mean flow pore diameter range and bubble pointpore diameter range. Still furthermore, by performing the gel processingin the presence of moisture at a temperature range of no less than thegelling temperature of the heat-and-humidity gelling resin and no morethan “the melting point of the heat-and-humidity gelling resin −20° C.”,it is made possible to perform the processing at a temperature that doesnot cause the heat-and-humidity gelling resin and the other componentfiber to substantially shrink, whereby a shrinkage phenomenon associatedwith melting of the heat-and-humidity gelling resin and the othercomponent fiber is suppressed. As a result, it is possible to obtain aseparator that has a small change in dimensions during processing of thenonwoven, small variations in the mass per unit area, the thickness andthe like, leading to an excellent yield and a small battery defect rate.

Particularly, when the heat-and-humidity gelling resin having such aproperty is used and is processed under a high pressure using a thermalroller or the like, the heat-and-humidity gelling resin on an entirenonwoven sheet is pressed and spread while being caused to beinstantaneously gelled, to penetrate into the nonwoven sheet. Therefore,the fiber constituting the nonwoven can be fixed substantially uniformlyin an in-plane direction and a thickness direction of the nonwoven usingthe gel material. As a result, a separator that has a large tensilestrength and puncture strength and an appropriate mean flow porediameter range and bubble point pore diameter range of the nonwoven, anda small variation in the puncture strength, can be obtained.

As used herein, the nonwoven sheet indicates a web and a nonwoven thatare in a form before gel processing. The web indicates a carded web, anairlaid web, a wetlaid web, or the like, in which component fibers arenot bonded together. The nonwoven is produced by a method in which theweb is subjected to an entanglement process, such as a bonding process(thermal bonding, etc.), a hydroentangling process, a needlepunchingprocess, or the like, so that component fibers are bonded together. Thesame is true of the following description.

The resin (heat-and-humidity gelling resin) capable of gelling byheating in the presence of moisture, which is used in the organicelectrolyte battery separator of the present invention, indicates aresin that gels and swells in the presence of moisture at a temperatureof 60° C. or more to become a gel material, thereby fixing otherfiber(s) constituting a nonwoven. Since batteries are used under variouscircumstances, the stability of the battery is deteriorated if the resingels at less than 60° C. Any resin that has such a property may be used.Among other things, an ethylene-vinyl alcohol copolymer having aspecific composition is particularly preferable in terms ofheat-and-humidity gel processing ability, water resistance, anddimensional stability during processing of a nonwoven.

The ethylene-vinyl alcohol copolymer is a copolymer that is obtained bysaponification of an ethylene-vinyl acetate copolymer. Thesaponification degree is preferably 95% or more. A more preferable lowerlimit of the saponification degree is 98%. When the saponificationdegree is less than 95%, the thread-forming ability is deteriorated whena fiber is produced. Also, gelation is likely to occur even at lowtemperature, likely leading to a trouble in fiber production and anonwoven processing step. Further, when incorporated into a battery, thechemical stability in electrolytic solution is poor, or the stability athigh temperature is deteriorated.

The ethylene-vinyl alcohol copolymer preferably has an ethylene contentin a range of 20 mol % to 50 mol %. A more preferable lower limit of theethylene content is 25 mol %. A more preferable upper limit of theethylene content is 45 mol %. When the ethylene content is less than 20mol %, the thread-forming ability is poor and the ethylene-vinyl alcoholcopolymer is likely to be softened, likely leading to a problem in fiberproduction and a nonwoven processing step. Further, when incorporatedinto a battery, the chemical stability in the electrolytic solution ispoor, or the stability at high temperature is deteriorated. On the otherhand, when the ethylene content exceeds 50 mol %, the heat-and-humiditygelling temperature is increased. In this case, the processingtemperature has to be increased up to about the melting point in orderto obtain a desired mean flow pore diameter and bubble point porediameter. As a result, there is a possibility that the dimensionstability of the nonwoven is adversely influenced.

The heat-and-humidity gelling resin may be in any form, includingpowder, emulsion, film, a single component fiber containing theheat-and-humidity gelling resin, a composite fiber containing acombination of the heat-and-humidity gelling resin and another resin,and the like. The heat-and-humidity gelling resin is likely in the formof a fiber in terms of a nonwoven production step. The fiber may haveany cross-sectional shape, including a circle, a hollow shape, anirregular shape, an ellipse, a star, a flat shape, and the like. Acircle is preferable in terms of ease of fiber production. The compositefiber may have any composite form, including a concentric sheath-coretype, an eccentric sheath-core type, a side-by-side type, a splittabletype, an islands-in-the-sea type, and the like. In the case of thecomposite fiber, it is important for the heat-and-humidity gelling resinto cover at least a portion of a surface of the fiber during gelprocessing of the heat-and-humidity gelling resin. Particularly, asplittable composite fiber in which the heat-and-humidity gelling resinand another resin other than the heat-and-humidity gelling resin aredisposed adjacent to each other is preferable. A cross-sectional shapeof the fiber is preferably of a radial type, a comb type, a matrix type,a laminar type, or the like, in which each segment is independent, interms of segmentation.

Also in the case of the splittable composite fiber made of theheat-and-humidity gelling resin and another resin, the other resin ispreferably not compatible with the heat-and-humidity gelling resin,although it may be highly compatible with the heat-and-humidity gellingresin. This is because the non-compatible resin can be detached andsplit so that the heat-and-humidity gelling fiber containing theheat-and-humidity gelling resin is changed into microfibers, whereby thecomponent fibers are fixed more uniformly, contributing to establishmentof an appropriate mean flow pore diameter range and bubble point porediameter range. The other resin is not particularly limited and may beany resin that is not compatible with the heat-and-humidity gellingresin. Among other things, the other resin is preferably polypropylene,polyethylene, polymethylpentane, or a copolymer thereof, or the like.Particularly, polypropylene is preferable in terms of fiber productionand stability with respect to battery electrolytic solution.

The heat-and-humidity gelling resin preferably accounts for 10 mass % to50 mass % of the whole separator. A more preferable lower limit of theheat-and-humidity gelling resin content is 15 mass %. An even morepreferable lower limit of the content is 20 mass %. A more preferableupper limit of the content is 45 mass %. An even more preferable upperlimit of the content is 40 mass %. A most preferable upper limit of thecontent is 35 mass %. When the heat-and-humidity gelling resin contentis less than 10 mass %, it is difficult for the gel material to bespread uniformly into the nonwoven and sufficiently penetrate betweenthe fibers, in spite of gel processing. As a result, it is difficult toobtain an appropriate mean flow pore diameter range and bubble pointpore diameter range, likely leading to a variation in the puncturestrength. Particularly, it is difficult to decrease the bubble pointpore diameter. Further, a portion in which the other fiber constitutingthe nonwoven is fixed is reduced, whereby there is a possibility thatthe puncture strength is also reduced. On the other hand, when theheat-and-humidity gelling resin content exceeds 50 mass %, a surface ofthe nonwoven is likely to become a film, so that the electrolyticsolution holding ability is reduced, and therefore, there is apossibility that an internal resistance of the battery is increased.Further, the heat-and-humidity gelling resin becomes likely to adhere toa roller or the like during gel processing, likely leading to poorperformance in a nonwoven production step.

The fiber constituting the nonwoven, other than the heat-and-humiditygelling resin, used in the battery separator of the present inventionpreferably has a fiber diameter of 15 μm or less. A more preferableupper limit of the fiber diameter is 14 μm. An even more preferableupper limit of the fiber diameter is 13 μm. On the other hand, the lowerlimit of the fiber diameter of the other fiber is not particularlylimited as long as the nonwoven production step can be performed in therange. Particularly taking into consideration the dispersion ability ofthe fiber in a wetlaying process, the fiber diameter is preferably 1 μmor more. When the fiber diameter of the other fiber exceeds 15 μm, it isdifficult to obtain an appropriate mean flow pore diameter and bubblepoint pore diameter of the nonwoven by gelation of the heat-and-humiditygelling resin. As a result, a fine powder short circuit is likely tooccur. As used herein, when a cross-section of a fiber is in the shapeof a circle, the fiber diameter refers to the diameter of the circle.When the cross-sectional shape is a non-circle, the fiber diameterrefers to a maximum thickness in a minor axis direction. The maximumthickness in the minor axis of a fiber whose cross-section is in theshape of a non-circle indicates a maximum height when the fiber isplaced, the way it is, with a major axis of the fiber being parallel toa horizontal plane. The term “the way it is” indicates that it isassumed that no external force is applied to the fiber other thangravity. Note that when it is difficult to determine a fiber diameterusing the above-described method, a fineness of a fiber is measured anda circular cross-section having such a fineness is assumed, and thediameter of the circle can be regarded as the fiber diameter.

The average fiber diameter of the other fiber constituting the nonwovenother than the heat-and-humidity gelling resin is preferably 10 μm orless. A more preferable upper limit of the average fiber diameter is 9μm. An even more preferable upper limit of the average fiber diameter is8 μm. On the other hand, a lower limit of the average fiber diameter ofthe other fiber is not particularly limited as long as the nonwoven canbe produced in the range. The average fiber diameter of the other fiberis preferably 1 μm or more for reasons of stability in fiber production.When the average fiber diameter exceeds 10 μm, it is difficult to obtaina separator having desired ranges of mean flow pore diameter and bubblepoint pore diameter. As a result, a fine powder short circuit or thelike is likely to occur.

Among the fibers constituting the nonwoven used in the organicelectrolyte battery separator of the present invention, a fibercontaining the heat-and-humidity gelling fiber in which theheat-and-humidity gelling resin constitutes a portion of fiber surfacepreferably has a fiber diameter of 15 μm or less. A more preferableupper limit of the fiber diameter is 14 μm. An even more preferableupper limit of the fiber diameter is 13 μm. All fibers constituting thenonwoven preferably have a diameter within this range. This is becausewhen the fiber diameter exceeds 15 μm, it is difficult to obtain thenonwoven having desired ranges of mean flow pore diameter and bubblepoint pore diameter during gel processing. On the other hand, a lowerlimit of the fiber diameter is not particularly limited as long as thenonwoven can be produced in the range. Particularly taking intoconsideration the dispersion ability of the fiber in a wetlayingprocess, the fiber diameter is preferably 1 μm or more.

Particularly, in order to obtain desired ranges of mean flow porediameter and bubble point pore diameter, when the heat-and-humiditygelling resin is a fiber, a fiber diameter of the heat-and-humiditygelling fiber is preferably small, specifically 6 μm or less. A morepreferable upper limit of the heat-and-humidity gelling fiber is 5 μm.An even more preferable upper limit of the heat-and-humidity gellingfiber is 4 μm. When the fiber diameter of the heat-and-humidity gellingfiber is 6 μm or less, the heat-and-humidity gelling fiber that becomesa gel material spreads to form a film without filling a gap betweenfibers more than necessary, so that other fiber(s) can be fixed. A lowerlimit of the fiber diameter of the heat-and-humidity gelling fiber isnot particularly limited. However, the fiber diameter of theheat-and-humidity gelling fiber is preferably 1 μm or more for reasonsof stability in production. To obtain such a microfine fiber, forexample, it is preferable that a splittable composite fiber containingthe heat-and-humidity gelling resin and its non-compatible resin isprovided and split. For example, an about 8- to 24-splittable type fiberspinning nozzle may be used to obtain a splittable composite fiber ofabout 0.5 to 3 dtex, which in turn may be split.

Also, when the heat-and-humidity gelling resin is a fiber, it isimportant for all fibers constituting the nonwoven to have an averagefiber diameter of 10 μm or less. A more preferable upper limit of theaverage fiber diameter is 9 μm. An even more preferable upper limit ofthe average fiber diameter is 8 μm. On the other hand, a lower limit ofthe average fiber diameter of all the fibers is not particularly limitedas long as the nonwoven can be produced in the range. The average fiberdiameter is preferably 1 μm or more for reasons of stability in fiberproduction. When the average fiber diameter exceeds 10 μm, it isdifficult to obtain a separator having desired ranges of mean flow porediameter and bubble point pore diameter. As a result, a fine powdershort circuit or the like is likely to occur.

It is also preferable that the other fiber constituting the organicelectrolyte battery separator of the present invention includes ahigh-strength fiber having a single fiber strength of 4.5 cN/dtex ormore for the purpose of increasing the puncture strength of the nonwovento further improve the dendritic short circuit prevention ability. Thesingle fiber strength of the high-strength fiber is more preferably 5cN/dtex or more, even more preferably 5.5 cN/dtex or more. When thesingle fiber strength is less than 4.5 cN/dtex, the other fiber is notlikely to contribute to the puncture strength, likely leading to adendritic short circuit. It is also preferable that the melting point ofthe high-strength fiber is greater than or equal to a temperature thatis lower by 20° C. than the melting point of the heat-and-humiditygelling resin. More preferably, the melting point of the high-strengthfiber is greater than or equal to a temperature that is lower by 15° C.than the melting point of the heat-and-humidity gelling resin. An upperlimit of the melting point of the high-strength fiber is notparticularly limited. For example, when the high-strength fiber is apolyolefin fiber, the melting point is preferably 250° C. or less. Whenthe melting point of the high-strength fiber is less than a temperaturethat is lower by 20° C. than the melting point of the heat-and-humiditygelling resin, shrinkage is likely to occur in association withsoftening or melting of a resin constituting the high-strength fiberduring gel processing, likely leading to occurrence of an irregular massper unit area, thickness, pore diameter or the like of the nonwoven. Asa result, the yield of the separator is reduced, or there is apossibility that a fine powder short circuit and a dendritic shortcircuit occur.

The resin constituting the high-strength fiber is selected from thosethat have the above-described properties, including polypropylene,polyethylene, ultrahigh molecular weight polyethylene, polyester, nylon,polyparaphenylene benzobisoxazole, carbon, and the like. Among theseresins, the polyolefin resins are preferable because they are quite easyto handle when an ethylene-vinyl alcohol copolymer is used as theheat-and-humidity gelling resin, and a desired battery characteristic isobtained. Particularly, polypropylene is preferable in terms of fiberproduction, stability of electrolytic solution, cost, and the like.Also, the high-strength fiber may be in any form of a single componentfiber, a composite fiber, and the like. A cross-sectional shape of thehigh-strength fiber is not limited to a circle, a hollow shape, anirregular shape, an ellipse, a star, a flat shape, and the like. Takingthe ease of fiber production into consideration, the cross-sectionalshape is preferably a circle. When the high-strength fiber is acomposite fiber, the cross-sectional shape may be of any of a concentricsheath-core type, an eccentric sheath-core type, a side-by-side type, anislands-in-the-sea type, a splittable type, and the like.

The proportion of the nonwoven occupied by the high-strength fiber ispreferably in a range of 5 to 250 parts by mass where theheat-and-humidity gelling resin is assumed to be 100 parts by mass. Amore preferable lower limit of the added amount is 10 parts by mass. Aneven more preferable lower limit of the added amount is 20 parts bymass. A more preferable upper limit of the added amount is 220 parts bymass. An even more preferable upper limit of the added amount is 200parts by mass. When the added amount of the high-strength fiber is lessthan 5 parts by mass, it is difficult for the high-strength fiber tocontribute to an improvement in the puncture strength, likely leading tothe occurrence of a dendritic short circuit. When the added amount ofthe high-strength fiber exceeds 250 parts by mass, the proportionoccupied by the heat-and-humidity gelling resin is small. In this case,it is difficult to obtain a small pore diameter, likely leading tooccurrence of a fine powder short circuit.

Also in the organic electrolyte battery separator of the presentinvention, the gel material is used to fix the fiber constituting thenonwoven. Therefore, no heat-melting fiber that does not become a gelunder heat and humidity has to be additionally contained. Alternatively,such a heat-melting fiber may be added for the purpose of simplificationof a nonwoven production step, an improvement in the tensile strength ofthe nonwoven, or the like. When a heat-melting fiber is added, apreferable added amount thereof is in a range of 10 to 300 parts by masswhere the amount of the heat-and-humidity gelling resin is assumed to be100 parts by mass. A more preferable lower limit of the added amount is20 parts by mass. An even more preferable lower limit of the addedamount is 30 parts by mass. A more preferable upper limit of the addedamount is 250 parts by mass. An even more preferable upper limit of theadded amount is 200 parts by mass. When the added amount of theheat-melting fiber is less than 10 parts by mass, it is difficult toobserve an effect of addition. On the other hand, when the added amountof the heat-melting fiber exceeds 300 parts by mass, the proportionoccupied by the heat-and-humidity gelling resin is small, whereby it isdifficult to reduce the pore diameter of the nonwoven, likely leading tothe occurrence of a fine powder short circuit.

The heat-melting fiber refers to a fiber that does not become a gel andmelts around its melting point (melting peak temperature) in thepresence of moisture to bond fibers. The heat-melting fiber isdistinguished from the heat-and-humidity gelling resin. Also, theheat-melting fiber is preferably a fiber that does not substantiallyshrink at a temperature that causes the heat-and-humidity gelling resinto become a gel (gel material) (hereinafter the temperature is referredto as a gel processing temperature). As used herein, the term “does notsubstantially shrink” in relation to a fiber indicates that an areashrinkage rate of the nonwoven during gel processing is less than 5%. Areason why the heat-melting fiber is defined as described above is thatwhen a nonwoven sheet containing moisture is subjected to gel processingwhere the temperature of the heat treatment device is set to be 100° C.or more, the actual temperature is likely to be lower than the settemperature and it may be difficult to accurately measure the actualtemperature (gel processing temperature). Therefore, it is distinguishedfrom the gel processing temperature, and the heat-melting fiber isassumed not to substantially shrink at the gel processing temperature.

The resin used in the heat-melting fiber is not particularly limited. Apolyolefin resin is preferable in terms of stability relative to theelectrolytic solution. The heat-melting fiber is in the form of a singlecomponent fiber, a composite fiber, or the like. Particularly, asheath-core composite fiber in which the sheath is made of a low-meltingpoint resin and the core is made of a resin having a higher meltingpoint than that of the sheath resin, is preferable. Examples of thesheath-core composite fiber include polypropylene/polyethylene,polypropylene/ethylene-propylene copolymer,polypropylene/ethylene-methyl acrylate copolymer,polypropylene/ethylene-vinyl acetate copolymer, and the like. Apreferable ratio of the core resin to the sheath resin is about 30:70 to70:30 (=core resin:sheath resin) (by volume). A fiber cross-sectionalshape of the sheath-core composite fiber may be of any of a concentricsheath-core type, an eccentric sheath-core type, a side-by-side type, anislands-in-the-sea type, and the like. The concentric sheath-core typeis particularly preferable.

Specifically, the nonwoven of the present invention comprises thefollowing component fibers: a splittable composite fiber that containsthe heat-and-humidity gelling resin and another resin, which areadjacent to each other in a cross-section of the fiber, to be able toprovide the heat-and-humidity gelling fiber; and other fibers that are ahigh-strength fiber having a single fiber strength of 4.5 cN/dtex ormore and a heat-melting fiber that does not substantially shrink at atemperature that causes the heat-and-humidity gelling resin under heatand humidity to gel and fix the other fibers, where, assuming that thesplittable composite fiber is 100 parts by mass, the high-strength fiberis in a range of 10 to 200 parts by mass and the heat-melting fiber isin a range of 10 to 200 parts by mass. In this case, a desired batterycharacteristic can be most effectively obtained. A more preferable rangeis such that, assuming that the splittable composite fiber is 100 partsby mass, the high-strength fiber is in a range of 12.5 to 75 parts bymass and the heat-melting fiber is in a range of 12.5 to 100 parts bymass.

The nonwoven of the present invention further may comprise a fiber inaddition to the above-described fibers. Also in this case, the fiber maybe in any form of a single component fiber, a composite fiber, and thelike. A cross-sectional shape thereof may be any of a circle, a hollowshape, an irregular shape, an ellipse, a star, a flat shape, and thelike. The cross-sectional shape is preferably a circle in terms of easeof fiber production. In the case of the composite fiber form, the fibermay be of any of a concentric sheath-core type, an eccentric sheath-coretype, a side-by-side type, an islands-in-the-sea type, a splittabletype, and the like. The fiber may be made of any resin. Polyolefins arepreferable in terms of stability of electrolytic solution.

Further, the fiber optionally may be supplemented as appropriate with anadditive, such as an antioxidant, a light stabilizer, an ultravioletabsorber, a neutralizer, a nucleating agent, a lubricant, an antistaticagent, a pigment, a plasticizer, a hydrophilizing agent, or the like, inan amount that does not prevent the effect of the present invention.

In addition to the heat-and-humidity gelling resin or theheat-and-humidity gelling fiber and the other fiber(s) constituting thenonwoven, a synthetic pulp preferably is added in order to reduce themean flow pore diameter and the bubble point pore diameter of thenonwoven. The synthetic pulp refers to a fiber-like material made of aso-called fibrillized, natural pulp-like synthetic resin, in which thefiber surface is divided into a number of branches. The synthetic pulpis distinguished from the other fiber of the present invention. Examplesof the resin constituting the synthetic pulp include polyethylene,polypropylene, and the like. The average fiber length of the syntheticpulp is preferably in a range of 0.5 mm to 2 mm. The average fiberlength of the synthetic pulp is used as an index for indicating a formof the synthetic pulp. Assuming that the nonwoven sheet is producedusing a wetlaying technique, when the average fiber length is less than0.5 mm, there is a possibility that a larger amount of the syntheticpulp drops out in a wetlaying step. When the average fiber lengthexceeds 2 mm, there is a possibility that the dispersion ability islowered during a wetlaying process. An example of a synthetic pulp thatsatisfies the above-described conditions, includes “SWP” EST-8, E400(tradename, manufactured by Mitsui Chemicals, Inc.) and the like.

Assuming the heat-and-humidity gelling resin is 100 parts by mass in thenonwoven, the synthetic pulp is preferably in a range of 10 to 200 partsby mass. A more preferable lower limit of the added amount is 20 partsby mass. A more preferable upper limit of the added amount is 150 partsby mass. When the added amount of the synthetic pulp is less than 10parts by mass, it is difficult to observe an effect from the addition.On the other hand, when the added amount of the synthetic pulp exceeds200 parts by mass, the proportion of the heat-and-humidity gelling resinis decreased, and therefore, there is a possibility that the puncturestrength is reduced.

Specifically, the nonwoven comprises the following component fibers: asplittable composite fiber that contains the heat-and-humidity gellingresin and another resin, which are adjacent to each other in across-section of the fiber, to be able to provide the heat-and-humiditygelling fiber; and other fibers that are the above-describedhigh-strength fiber and a heat-melting fiber that does not substantiallyshrink at a temperature that causes the heat-and-humidity gelling resinunder heat and humidity to gel and fix the other fibers, where, assumingthat the splittable composite fiber is 100 parts by mass, thehigh-strength fiber is in a range of 6.25 to 120 parts by mass and theheat-melting fiber is in a range of 12.5 to 120 parts by mass; and inaddition, the above-described synthetic pulp that is in a range of 6.25to 120 parts by mass. In this case, a desired battery characteristic canbe obtained most effectively and the thickness can be reduced mosteffectively. More preferably, assuming that the splittable compositefiber is 100 parts by mass, the high-strength fiber is in a range of 7to 100 parts by mass, the heat-melting fiber is 15 to 115 parts by mass,and the synthetic pulp is 15 to 100 parts by mass.

The organic electrolyte battery separator of the present invention needsto have a mean flow pore diameter in a range of 0.3 μm to 5 μm, and abubble point pore diameter in a range of 3 μm to 20 μm. A morepreferable lower limit of the mean flow pore diameter is 0.4 μm. An evenmore preferable lower limit of the mean flow pore diameter is 0.5 μm. Amore preferable upper limit of the mean flow pore diameter is 4.5 μm. Aneven more preferable upper limit of the mean flow pore diameter is 4 μm.On the other hand, a more preferable lower limit of the bubble pointpore diameter is 4 μm. An even more preferable lower limit of the bubblepoint pore diameter is 5 μm. A more preferable upper limit of the bubblepoint pore diameter is 15 μm. An even more preferable upper limit of thebubble point pore diameter is 13 μm. A most preferable upper limit ofthe bubble point pore diameter is 10 μm. By satisfying these conditionssimultaneously, it is possible to obtain a separator that has anexcellent level of fine powder short circuit prevention ability anddendritic short circuit prevention ability. When the mean flow porediameter is less than 0.3 μm or the bubble point pore diameter is lessthan 3 μm, the electrolytic solution holding ability is deteriorated,likely leading to a large internal resistance of the battery. On theother hand, when the mean flow pore diameter exceeds 5 μm or the bubblepoint pore diameter exceeds 20 μm, a fine powder short circuit and adendritic short circuit are likely to occur.

The organic electrolyte battery separator of the present inventionpreferably has a mean flow pore diameter reduction rate of 60% or more.The mean flow pore diameter reduction rate (%) is represented by:mean flow pore diameter reduction rate (%)={(X−X _(B))/X}×100where X_(B) represents a mean flow pore diameter of the nonwoven aftergel processing of the heat-and-humidity gelling resin and X represents amean flow pore diameter of the nonwoven sheet before gel processing.

The mean flow pore diameter reduction rate is an index for indicatinghow much the heat-and-humidity gelling resin is pressed and spread toform a gel material when the nonwoven sheet (starting material beforegel processing) containing the heat-and-humidity gelling resin issubjected to gel processing, i.e., an index for indicating a degree ofgelation. A more preferable lower limit of the mean flow pore diameterreduction rate is 70%. A preferable upper limit of the mean flow porediameter reduction rate is 95%. When the mean flow pore diameterreduction rate is less than 60%, the heat-and-humidity gelling resindoes not substantially uniformly become a gel, whereby there is apossibility that a desired puncture strength is not obtained. When themean flow pore diameter reduction rate exceeds 95%, a gap of theseparator is small. As a result, the electrolytic solution permeabilityis lowered, whereby there is a possibility that the internal resistanceof the battery is increased.

In the organic electrolyte battery separator of the present invention,the heat-and-humidity gelling resin is pressed and spread while gellingunder heat and humidity, and the gel material fills a gap between fibersconstituting the nonwoven to fix the other fiber. In this case, the gelmaterial preferably is formed into a film that partially covers asurface of the nonwoven. The proportion of the entire surface of thenonwoven occupied by the film (film degree) is preferably in a range of40% to 90%. A more preferable lower limit of the film degree is 45%. Aneven more preferable lower limit of the film degree is 50%. A preferableupper limit of the film degree is 80%. An even more preferable upperlimit of the film degree is 70%. The film degree is an index forindicating a degree of spread of the gel material, i.e., an index forindicating a degree of penetration between fibers. A larger film degreeindicates that the gel material is substantially uniformly spread on asurface and an inside of the nonwoven. When the film degree is less than40%, penetration of the gel material between fibers is insufficient. Inthis case, it is difficult to obtain an appropriate mean flow porediameter range and bubble point pore diameter range, and particularlythe bubble point pore diameter is likely to be large. As a result, afine powder short circuit is likely to occur. On the other hand, whenthe film degree exceeds 90%, a region in which the film covers thenonwoven to remove pores is likely to be increased. As a result, theelectrolytic solution permeability is deteriorated, whereby there is apossibility that the internal resistance of the battery is increased.

Particularly, in order to obtain a separator having an appropriate meanflow pore diameter range and bubble point pore diameter range as in thepresent invention, it is important to cause the heat-and-humiditygelling resin existing throughout the nonwoven sheet to gel moreuniformly during gel processing. To achieve this, it is important touniformly provide moisture into the entire nonwoven sheet including itsinside before gel processing. In other words, it is important for thenonwoven sheet to have water wettability more uniformly. An example ofan index for indicating the water wettability is a contact angle ofdechlorinated water. The smaller the contact angle, the higher the waterwettability, i.e., moisture can be provided more uniformly to thenonwoven sheet. Specifically, the contact angle of the dechlorinatedwater on the nonwoven sheet surface before gel processing is preferably60 degrees or less five seconds after dropping of the dechlorinatedwater. A more preferable contact angle is 55 degrees or less. An evenmore preferable contact angle is 50 degrees or less. When the contactangle of the dechlorinated water on the nonwoven sheet surface exceeds60 degrees, the water wettability is likely to be insufficient, so thatit is difficult to provide moisture uniformly.

When a hydrophobic fiber, such as a polyolefin resin, is used in theseparator of the present invention, it is likely that the waterwettability is insufficient and it is difficult to provide moistureuniformly. Therefore, it is preferable to subject the nonwoven sheet toa hydrophilic treatment. Examples of the hydrophilic treatment include acorona discharge treatment, a plasma treatment, an electron beamtreatment, a treatment of exposure to fluorine atmosphere (hereinafterreferred to as a fluorine treatment), a graft treatment, a sulfonationtreatment, a surfactant treatment, and the like.

For example, in the case of the corona discharge treatment, both sidesof the nonwoven sheet each are treated 1 to 20 times, where a totaldischarge amount is in a range of 0.05 to 10 k W·min/m². In the case ofthe fluorine treatment, for example, a hydrophilic group is introducedinto the nonwoven sheet by contacting with a gas mixture of fluorine gasdiluted with inert gas, and oxygen gas or sulfur dioxide gas. In thecase of the graft polymerization treatment, the nonwoven sheet isimmersed in a solution containing a vinyl monomer and a polymerizationinitiator, followed by heating, or a vinyl monomer is applied onto thenonwoven sheet before applying radiation. More preferably, by modifyingthe quality of the nonwoven sheet surface using ultraviolet irradiation,corona discharge, plasma discharge, or the like before contacting thevinyl monomer solution and the nonwoven sheet, graft polymerization canbe performed efficiently. Examples of the sulfonation treatment includea concentrated sulfuric acid treatment, a fuming sulfuric acidtreatment, a chlorosulfuric acid treatment, an anhydrous sulfuric acidtreatment, and the like. In the case of the surfactant treatment, thenonwoven sheet is immersed in a solution of a hydrophilic anionsurfactant or a nonion surfactant, or the surfactant is attached to thenonwoven sheet by application, for example. Note that theabove-described hydrophilic treatment may be applied to the nonwovenafter gel processing. Any two or more of the above-described treatmentmethods may be combined.

Among the hydrophilic treatments, the fluorine treatment is particularlypreferable since moisture can be provided more uniformly up to theinside of the nonwoven sheet during gel processing. Further, thefluorine treatment can introduce a hydrophilic group deeper from theresin surface, so that a reduction in hydrophilicity is small after gelprocessing, i.e., the hydrophilicity of the nonwoven can be maintainedafter gel processing. As a specific condition of the fluorine treatment,the fluorine concentration of the gas mixture in the fluorine treatmentis preferably in a range of 0.01 to 80 volume %. A more preferable lowerlimit of the fluorine concentration is 0.1 volume %. An even morepreferable lower limit of the fluorine concentration is 0.5 volume %. Amore preferable upper limit of the fluorine concentration is 30 volume%. An even more preferable upper limit of the fluorine concentration is10 volume %. The reaction temperature is preferably in a range of 10° C.or more and 50° C. or less. The reaction time is preferably in a rangeof 1 second or more to 30 minutes, though not particularly limited.

In the organic electrolyte battery separator of the present invention,the contact angle of dechlorinated water on the nonwoven surface ispreferably 60 degrees or less five seconds after dropping of thedechlorinated water. A more preferable contact angle is 55 degrees orless. A more preferable contact angle is 50 degrees or less. The contactangle serves as an index for indicating a degree of reduction in waterwettability due to gel processing. A hydrophilic treatment that canmaintain the contact angle at 60 degrees or less after gel processing,is preferable since moisture can be provided up to the inside of thenonwoven sheet of the present invention before gel processing. Such ahydrophilic treatment that can maintain the contact angle at 60 degreesor less after gel processing includes a fluorine treatment as describedabove, though any treatment having a similar effect can be used.

The organic electrolyte battery separator of the present inventionpreferably has a puncture strength of 2 N or more. A more preferablelower limit of the puncture strength is 2.2 N. The puncture strength isa substitute characteristic for indicating the level of dendritic shortcircuit prevention ability. The greater the puncture strength, the moreunlikely a dendritic short circuit occurs. When the puncture strength isless than 2 N, a dendritic short circuit is likely to occur. A standarddeviation of the puncture strength is preferably 1.1 N or less, morepreferably 1 N or less, and even more preferably 0.9 N or less. Thestandard deviation of the puncture strength is an index for indicating avariation in the puncture strength. The greater the standard deviationof the puncture strength, the more likely a dendritic short circuitoccurs since there is a portion having a small puncture strength. Whenthe standard deviation exceeds 1.1 N, a dendritic short circuit islikely to occur as described above.

An index for indicating a variation in the puncture strength, which iscalculated based on the puncture strength and the standard deviation ofthe nonwoven according to the following expression, is preferably 0.165or less:“puncture strength variation index=standard deviation/puncturestrength”.

The variation index is calculated based on the standard deviation usingthe average of the puncture strength as a reference. The smaller thevariation index value, the closer the variation index value is to theaverage, i.e., it is indicated that the variation is small. Such a smallvariation index (parameter) is achieved by causing the heat-and-humiditygelling resin to become a gel that is in turn pressed and spread andcausing the resultant gel material to fix the other fiber, as in thepresent invention.

The organic electrolyte battery separator of the present inventionpreferably has a thickness in a range of 15 μm to 80 μm. A morepreferable lower limit of the thickness is 20 μm. An even morepreferable lower limit of the thickness is 25 μm. A more preferableupper limit of the thickness is 70 μm. An even more preferable upperlimit of the thickness is 60 μm. When the thickness of the separator isless than 15 μm, a pore diameter of the separator, particularly a bubblepoint pore diameter thereof, is likely to be increased, whereby there isa possibility that the fine powder short circuit prevention ability andthe dendritic short circuit prevention ability are reduced. On the otherhand, when the thickness of the separator exceeds 80 μm, theelectrolytic solution permeability is deteriorated, so that there is apossibility that the internal resistance of the battery is increased.Further, the number of electrodes per volume of the battery is reduced,likely leading to poor battery performance.

A specific volume of the nonwoven in the organic electrolyte batteryseparator of the present invention is preferably in a range of 1.2 cm³/gto and 2.5 cm³/g. A more preferable lower limit of the specific volumeis 1.3 cm³/g. An even more preferable lower limit of the specific volumeis 1.4 cm³/g. A more preferable upper limit of the specific volume is2.3 cm³/g. An even more preferable upper limit of the specific volume is2.1 cm³/g. When the specific volume is less than 1.2 cm³/g, the nonwovenis excessively dense, so that the electrolytic solution holding abilityis poor. As a result, there is a possibility that the internalresistance of the battery is increased. On the other hand, when thespecific volume exceeds 2.5 cm³/g, the size of the nonwoven isexcessively large, so that it is difficult to obtain a small porediameter in the separator. As a result, a fine powder short circuit islikely to occur.

An mass per unit area of the nonwoven in the organic electrolyte batteryseparator of the present invention is preferably in a range of 10 to 50g/m². A more preferable lower limit of the mass per unit area of thenonwoven is 15 g/m². An even more preferable lower limit of the mass perunit area of the nonwoven is 20 g/m². A more preferable upper limit ofthe mass per unit area of the nonwoven is 45 g/m². An even morepreferable upper limit of the mass per unit area of the nonwoven is 40g/m². When the mass per unit area of the nonwoven is deviated from theabove-described range, it is difficult to obtain an intended separatorthickness and pore diameter.

Next, the organic electrolyte battery separator of the present inventionwill be described while indicating a production method thereof. Firstly,when the heat-and-humidity gelling resin is in the form of a fiber, aheat-and-humidity gelling fiber and other fiber(s) are prepared, and anonwoven sheet is produced using a known technique. The average fiberdiameter of the nonwoven sheet is preferably 10 μm or less. The reasonis described above.

Next, the nonwoven sheet optionally can be caused to be a hydrophilicnonwoven sheet by the above-described hydrophilic treatment. Byproviding moisture to the nonwoven sheet or the hydrophilic nonwovensheet, a water-containing sheet is produced. In order to obtain theseparator of the present invention, it is not necessary to cause theheat-and-humidity gelling resin to absorb up to an inside thereof.Moisture only needs to be attached around the heat-and-humidity gellingresin. By sandwiching the thus-constructed water-containing sheetbetween heating bodies with a method as described below, vapor thatinstantaneously occurs is confined in the nonwoven sheet by the heatingbodies, so that the heat-and-humidity gelling resin can be caused toinstantaneously gel inward as far as an inside of the nonwoven sheet.

A proportion of moisture provided to the hydrophilic nonwoven sheet ispreferably in a range of 20 to 300 mass %. A more preferable lower limitof the moisture proportion is 30 mass %. An even more preferable lowerlimit of the moisture proportion is 40 mass %. A more preferable upperlimit of the moisture proportion is 200 mass %. An even more preferableupper limit of the moisture proportion is 150 mass %. When the moistureproportion is less than 20 mass %, gelation of the heat-and-humiditygelling fiber is not sufficient, so that it is likely to be difficult tocause the gel material to penetrate between component fibers. As aresult, there is a possibility that the heat-and-humidity gelling fiberhas difficulty in contributing to obtaining an appropriate mean flowpore diameter range and bubble point pore diameter range. On the otherhand, when the moisture proportion exceeds 300 mass %, it is unlikelythat heat is applied uniformly to the surface and inside of the nonwovensheet during gel processing, so that there is a possibility that onlythe nonwoven surface becomes a film. As a result, the degree of gelationin a thickness direction of the resultant separator is not uniform, sothat fixation of the other component fiber(s) is not uniform. As aresult, there is a possibility that the irregularity of a pore diameterin the thickness direction is large. Moisture may be applied by any ofspraying, dipping into a water tank, and the like.

The water-containing sheet is subjected to a heat-and-humidity treatment(gel processing) using a heat treatment device that is set to be at atemperature in a range of no less than a temperature that causes theheat-and-humidity gelling resin to gel and no more than “the meltingpoint of the heat-and-humidity gelling resin −20° C.”. As a result, theheat-and-humidity gelling resin becomes a gel and the resultantheat-and-humidity gelling resin gel fixes the other fiber, therebyobtaining an organic electrolyte battery separator. The set temperatureduring gel processing is preferably at least 60° C. and not more than“the melting point of the heat-and-humidity gelling resin −20° C.”. Amore preferable lower limit of the set temperature is 80° C. An evenmore preferable lower limit of the set temperature is 85° C. A morepreferable upper limit of the set temperature is 140° C. An even morepreferable upper limit of the set temperature is 135° C. When the settemperature of gel processing is less than 80° C., it is difficult toobtain sufficient gelation. In this case, fixation of the othercomponent fiber is not sufficient, or there is a possibility that it isdifficult to obtain an appropriate mean flow pore diameter range andbubble point pore diameter range. On the other hand, when the settemperature of gel processing exceeds “the melting point of theheat-and-humidity gelling resin −20° C.”, if a thermal roller is usedduring gel processing, the heat-and-humidity gelling resin is likely toadhere to the roller, or the nonwoven shrinks, resulting in adeterioration in the dimension stability or the like. Therefore, theyield is likely to be lowered and the battery defect rate is likely tobe increased. A reason why the temperature of gel processing is regardedas the set temperature is as follows. When the water-containing nonwovensheet is subjected to gel processing, moisture in the nonwoven sheetfirstly is evaporated where the temperature of the heat treatment deviceis set to be 100° C. or more. In this case, the heat-and-humiditygelling resin proceeds with gelling, so that an actual temperature ofgel processing is likely to be lower than the set temperature.Therefore, it may be difficult to exactly determine the gel processingtemperature. Therefore, even when the melting point of the other fiberis lower than the set temperature of the heat treatment device, theother fiber may not be substantially melted or may not be substantiallyshrunk. Therefore, the gel processing temperature is preferably atemperature that does not cause the other fiber to substantially shrink.

The gel processing is preferably pressure processing using a thermalroller, a thermal press or the like. According to press processing, whenthe heat-and-humidity gelling resin is caused to gel under heat andhumidity, the gel material is pressed and spread to penetrate readilybetween fibers, so that an appropriate mean flow pore diameter andbubble point pore diameter can be obtained. Particularly, the pressprocessing is more preferably performed using a thermal roller becauseof an excellent level of productivity.

The thermal roller preferably has a line pressure in a range of 350 to10000 N/cm. A more preferable lower limit of the line pressure is 400N/cm. A more preferable upper limit of the line pressure is 9000 N/cm.When the line pressure is less than 350 N/cm, it is difficult to causethe heat-and-humidity gelling resin to penetrate sufficiently to theinside of the nonwoven, and also, it is difficult to cause the gelmaterial on the nonwoven surface to become a film. As a result, it isdifficult for the heat-and-humidity gelling resin to contribute toobtaining of an appropriate mean flow pore diameter range and bubblepoint pore diameter range, likely leading to the occurrence of a finepowder short circuit. On the other hand, when the line pressure exceeds10000 N/cm, the pressure is excessively high, so that the fiber islikely to be cut and a through-hole is likely to occur. As a result, afine powder short circuit is likely to occur, or there is a possibilitythat the puncture strength of the separator is lowered. When theheat-and-humidity gelling resin adheres to the thermal roller during gelprocessing, a release agent, such as a surfactant or the like, may beoptionally employed, for example. Further, an oiling agent, a sizingagent or the like may be added in an amount such that the nonwoven aftergel processing does not lose the effect of the present invention.

On the other hand, the heat-and-humidity gelling resin may be in theform of powder, emulsion or the like other than fiber. In this case, theheat-and-humidity gelling resin can be, for example, attached to thenonwoven sheet when the nonwoven sheet, which has been prepared, iscaused to be a water-containing sheet.

Further, a specific exemplary method of producing the organicelectrolyte battery separator of the present invention will bedescribed. Initially, the heat-and-humidity gelling fiber and otherfiber(s) are prepared. A nonwoven sheet having an average fiber diameterof 10 μm or less is produced using a known technique. Examples of theform of the nonwoven sheet include a drylaid web or a drylaid nonwovenobtained by, representatively, a carding method or an air-laying method,and a wetlaid web or a wetlaid nonwoven obtained by a wetlaying method.To obtain a more uniform nonwoven, a wetlaid web or a wetlaid nonwoven(hereinafter referred to as a wetlaid nonwoven sheet) obtained by awetlaying method is preferable.

A fiber length of a fiber for use in the wetlaid nonwoven sheet ispreferably in a range of 1 mm to 20 mm. A more preferable lower limit ofthe fiber length is 2 mm. An even more preferable lower limit of thefiber length is 3 mm. A more preferable upper limit of the fiber lengthis 15 mm. An even more preferable upper limit of the fiber length is 12mm. When the fiber length is less than 1 mm, the puncture strength ispoor. As a result, a dendritic short circuit is likely to occur. Whenthe fiber length exceeds 20 mm, the dispersion ability of the fiber inslurry is deteriorated, so that it is difficult to obtain a nonwovenhaving uniform texture. As a result, a large bubble point pore diameteris particularly likely to occur, likely leading to the occurrence of afine powder short circuit.

In the case of the wetlaid nonwoven sheet, an ordinary method may beused. Each fiber is mixed to a desired range, and is dispersed in waterto a concentration of 0.01 to 0.6 mass %, to adjust a slurry. In thiscase, a small amount of dispersing agent may be added. When a splittablecomposite fiber is used as a fiber constituting the slurry, the fiber issplit during beating and disintegration of the slurry. In this case, thesplittable fiber is more uniformly dispersed in the nonwoven during awetlaying process, so that the gel material is substantially uniformlypressed and spread during gel processing. As a result, it is possible toobtain a denser separator with an appropriate mean flow pore diameterand bubble point pore diameter and a small variation in the puncturestrength. Particularly, when a splittable composite fiber having theheat-and-humidity gelling resin is used and the fiber is split duringbeating and disintegration of the slurry, the heat-and-humidity gellingfiber that has been changed to a microfine fiber can be dispersed in thenonwoven more uniformly during the wetlaying process. As a result, whenthe heat-and-humidity gelling fiber is caused to become a gel, the gelis pressed and spread to penetrate between fibers and the gel materialfixes the component fiber substantially uniformly. Thereby, the meanflow pore diameter and the bubble point pore diameter are caused to bemore appropriate, so that a separator having a large puncture strengthand a small variation in puncture strength is likely to be obtained. Asa result, it is possible to obtain a separator that has an excellentlevel of fine powder short circuit prevention ability and dendriticshort circuit prevention ability. The slurry is caused to have a desiredmass per unit area using a papermaking machine of a short wire type, acylinder type, a fourdrinier type, or a combination thereof.

The web or the nonwoven may be subjected to a hydroentangling process toan extent such that the effect of the present invention is notprevented. When a splittable composite fiber is used as a componentfiber, the hydroentangling process promotes the splittable compositefiber to be split, so that the degree of entanglement between fibers isincreased.

Next, the wetlaid nonwoven sheet is subjected to the hydrophilictreatment to produce a hydrophilic nonwoven sheet. Moisture is providedto the hydrophilic nonwoven sheet to a moisture proportion in a range of20 to 300 mass %, resulting in a water-containing sheet. Thereafter, thewater-containing sheet is subjected to gel processing using a thermalroller that is heated to at least 60° C. and not more than a temperatureof “the melting point of the heat-and-humidity gelling resin −20° C.”under a line pressure of 350 to 10000 N/cm. With the above-describedprocess, it is preferably possible to obtain an appropriate mean flowpore diameter range and bubble point pore diameter range of theseparator and achieve a small variation in the puncture strength.

Note that the nonwoven for use in the present invention may be usedsingly, or alternatively, optionally may be laminated with anothersheet, such as, for example, a fine-porous film, other nonwovens, or thelike.

In the organic electrolyte battery separator of the present invention, aresin capable of gelling by being heated in the presence of moisture iscaused to gel under heat and humidity and the resultant gel material isused to fix other fiber(s) constituting the nonwoven, thereby making itpossible to obtain a desired mean flow pore diameter and bubble pointpore diameter. As a result, it is possible to obtain an organicelectrolyte battery having an excellent level of safety, less frequentshort circuits, and an excellent battery characteristic. Further, withthe above-described structure, the nonwoven has substantially noshrinkage, i.e., substantially no change in a dimension of the nonwoven,when subjected to thermal processing. Therefore, it is possible toobtain a separator in which an appropriate mean flow pore diameter rangeand bubble point pore diameter range can be obtained, the puncturestrength is large, and a variation in the puncture strength is small.Further, it is possible to provide an inexpensive organic electrolytebattery separator in which the yield is excellent, the battery defectrate is low, and particularly, the short circuit prevention ability isexcellent.

The organic electrolyte battery separator of the present invention isproduced by a method in which the nonwoven sheet containing theheat-and-humidity gelling resin and other fiber(s) is impregnated withwater and is subjected to gel processing at a temperature range of noless than a temperature that causes the heat-and-humidity gelling resinto gel and no more than “the melting point of the heat-and-humiditygelling resin −20° C.”. As a result, a separator that achieves a desiredmean flow pore diameter and bubble point pore diameter can be obtained.By subjecting the nonwoven sheet containing the heat-and-humiditygelling resin and the other fiber to a hydrophilic treatment before gelprocessing, the entire nonwoven sheet can hold moisture uniformly,leading to uniform gelation of the heat-and-humidity gelling resin.Further, when thermal press processing is employed as gel processing,the substantially uniformly-dispersed heat-and-humidity gelling resin iscaused to become a gel, which is in turn pressed and spread, and theresultant gel material can fix the other component fiber inward to theinside of the nonwoven substantially uniformly.

EXAMPLES

Hereinafter, the present invention will be specifically described by wayof examples. Note that the melting point, the single fiber fineness, thesingle fiber strength, the thickness, the puncture strength, thestandard deviation of puncture strengths, the mean flow pore diameter,the bubble point pore diameter, the film degree of nonwoven surface, thecontact angle of the nonwoven, and the area shrinkage ratio of thenonwoven (hereinafter referred to as “processing shrinkage ratio”) weremeasured by the following techniques:

(1) Melting point: measured in accordance with JIS K 7121 (DSC method).

(2) Single fiber fineness: measured in accordance with JIS L 1013.

(3) Single fiber strength: measured in accordance with JIS L 1015; atensile tester was used to measure the value of the load at which afiber is broken where a length between clamps of the sample was 20 mm,and the single fiber strength is represented by the load value.

(4) Thickness: thicknesses were measured at 10 different points for eachof three samples under a load of 175 kpa (measured using a micrometer inaccordance with JIS-B-7502) and the average value of a total of the 30points was calculated.

(5) Puncture strength: a nonwoven was cut out into a size of 30 mm(length)×100 mm (width); on the sample thus prepared, an aluminum pressplate (length: 46 mm, width: 86 mm, thickness: 7 mm) having a 11mm-diameter hole in its middle was placed; a peak load (N) was measuredwhen a needle was caused to pierce the middle hole of the press platevertically with a speed of 2 mm/sec, where the needle is in the shape ofa cone 18.7 mm in height with a ball-shaped tip portion of 1 mm diameterand a shaft having a base diameter of 2.2 mm, and a “KES-G5 HandyCompression Tester” manufactured by Kato Tech Co., Ltd. was used; andthe puncture strength is represented by the peak load. Note thatpuncture strengths were measured at 15 different points of each of foursamples and the average value of all 60 points was calculated.

(6) Standard deviation of puncture strengths: a standard deviation ofthe above-described puncture strengths was calculated where n=60.

(7) Mean flow pore diameter•bubble point pore diameter: measured by thebubble point method using a permporometer (manufactured by PorousMaterials Inc.) in accordance with ASTM F 316 86.

(8) Film degree of nonwoven surface: a surface of a nonwoven isphotographed using an electronic microscope at 200× magnification on 10arbitrary points. For example, as shown in FIGS. 3A to 3D, thepercentage of the area of adjacent fibers continuously fixed on thenonwoven surface was calculated with respect to the entire area of thenonwoven.

(9) Contact angle of nonwoven sheet surface: a contact angle meter(cleanliness evaluation system, type CA-X150, manufactured by KyowaInterface Science Co., Ltd.) is used. As shown in FIG. 1, a sample 2 of1 cm (length)×5 cm (width) is placed and fixed to a glass plate 1 with atape. Next, 2 microliters of pure water 3 are precisely dropped onto thesample 2 using a microsyringe. After being allowed to stand for 5seconds, a diameter a and a height h of the water drop of FIG. 1 aremeasured. The contact angle θ is calculated based on the diameter a andthe height h using the following expression:tan(θ/2)=h/(a/2).

(10) Processing shrinkage ratio (%): calculated using the followingexpression:{1−(post-gel processing nonwoven area/pre-gel processing nonwoven sheetarea)}×100.

(11) Battery characteristics

Short Circuit Characteristics

Eighty separators were laminated and incorporated between the positiveand negative electrodes of an E6 battery (15 cm×15 cm, rectangulartype), thereby producing a lithium ion secondary battery. Beforeinjection of electrolytic solution, when a mega electrical resistancemeter did not display ∞, it was determined that there is a shortcircuit, or when ∞ was displayed, it was determined that there was noshort circuit.

Safety

Eighty separators were laminated and incorporated between the positiveand negative electrodes of an E6 battery (15 cm×15 cm, rectangulartype), thereby producing a lithium ion secondary battery having anelectric capacity of 39.11 Ah (when discharging a 0.5-C constantcurrent). Initially, charging was started under conditions such that thecharging current was 10 A and the set upper voltage limit was 20 V.Generation of gas in the battery and damage of the battery pack wereobserved and evaluated when overcharging.

Self-Discharge Amount

Eighty separators were laminated and incorporated between the positiveand negative electrodes of an E6 battery (15 cm×15 cm, rectangulartype), thereby producing a lithium ion secondary battery.

The resultant battery was charged to a predetermined voltage (startingvoltage). Thereafter, the battery was allowed to stand in a 25° C.constant temperature bath for four weeks. After four weeks, the voltagewas measured. A difference between the starting voltage and the voltageafter four weeks was defined as a self-discharge amount.

Electric Capacity•Output Characteristics

Eighty separators were laminated and incorporated between the positiveand negative electrodes of an E6 battery (15 cm×15 cm, rectangulartype), thereby producing a lithium ion secondary battery having anelectric capacity of 42.41 Ah (when charging/discharging a 0.5-Cconstant current/constant voltage). Electric capacities that wereobtained when charging/discharing 1.0-C, 4.0-C or 6.0-C constantcurrent/constant voltage, and the proportion of an electric capacityobtained at each rated capacity where 42.41 Ah is regarded as 100%, wereobtained (output characteristics). When the output characteristic was80% or more at 6.0 C, the battery was accepted.

Fiber materials used in the examples and comparative examples wereprepared as follows.

Fiber 1

A first component was a heat-and-humidity gelling resin that was anethylene-vinyl alcohol copolymer having an ethylene content of 38 mol %and a saponification degree of 99% (EVOH, Soarnol K3835BN, melting point170° C., manufactured by The Nippon Synthetic Chemical Industry Co.,Ltd.). A second component was polypropylene (PP, SA03B, melting point163° C., manufactured by Japan Polychem Corporation). These componentswere melted and formed into a fiber using a known technique, and thefiber was stretched by a factor of three in air at 150° C., so that asplittable composite fiber was prepared that had a 16-radially segmentedcross-sectional shape, a first component/second component area ratio of50/50, and a fiber length of 6 mm.

Fiber 2

A first component was high-density polyethylene (HDPE, HE490, meltingpoint 132° C., manufactured by Japan Polychem Corporation). A secondcomponent was polypropylene (SA03B, melting point 163° C., manufacturedby Japan Polychem Corporation). These components were melted and formedinto a fiber using a known technique, and the fiber was stretched by afactor of five in hot water of 90° C., so that a splittable compositefiber was prepared that had a 16-radially segmented cross-sectionalshape, a first component/second component area ratio of 50/50, and afiber length of 6 mm.

Fiber 3

A sheath component was high-density polyethylene (HE490, melting point132° C., manufactured by Japan Polychem Corporation). A core componentwas polypropylene (SA03B, melting point 163° C., manufactured by JapanPolychem Corporation). These components were melted and formed into afiber using a known technique, and the fiber was stretched by a factorof four in hot water of 90° C., so that a concentric sheath-corecomposite fiber was prepared that had a core component/sheath componentarea ratio of 50/50 and a fiber length of 10 mm.

Fiber 4

A polypropylene (SA03B, melting point 163° C., manufactured by JapanPolychem Corporation) was melted and formed into a fiber, and the fiberwas stretched by a factor of three in air of 150° C. so that acircular-cross-sectional polypropylene single component fiber wasprepared that had a single fiber strength of 5.8 cN/dtex and a fiberlength of 10 mm.

Synthetic Pulp

As a synthetic pulp, a polyethylene synthetic pulp (trade name: SWPEST-8, manufactured by Mitsui Chemicals, Inc.) was prepared.

Example 1

50 mass % of the fiber 1 having a fineness of 1.4 dtex (post-splitminor-axis thicknesses: 2.57 μm (PP), 2.66 μm (EVOH)), 30 mass % of thefiber 3 of 0.8 dtex (fiber diameter: 10.3 μm), and 20 mass % of thefiber 4 of 0.6 dtex (fiber diameter: 8.37 μm) were mixed to prepare awater-dispersed slurry to a concentration of 0.5 mass %. From thewater-dispersed slurry thus obtained, wetlaid webs having an mass perunit area of 15 g/m² was produced using a cylinder type wet papermakingmachine and a short wire type wet papermaking machine. The two webs werecombined together. Next, a thermal treatment was performed at 135° C.using a cylinder dryer for drying, and at the same time, theheat-and-humidity gelling resin of the fiber 1 and the sheath componentof the fiber 4 temporarily bonded the fibers. The wetlaid nonwoven sheethaving an mass per unit area of 30 g/m² was rolled up. In the resultantwetlaid nonwoven sheet, substantially 100% of the fiber 1 was split andsubstantially uniformly dispersed in the nonwoven. Note that the splitratio was obtained as follows. The nonwovens were bundled in a mannersuch that the bundle has a cross-section in a longitudinal direction ofthe nonwoven. The bundle of the nonwoven fibers was passed through ametal plate having a 1-mm diameter hole. The resultant nonwoven wasmagnified by a factor of 400 using an electric microscope. Theproportion of splittable fibers was calculated.

Next, the wetlaid nonwoven sheet was treated at room temperature (25°C.) for one minute in a processing chamber into which a gas mixtureconsisting of 1 volume % of fluorine, 73 volume % of oxygen, and 26volume % of nitrogen had been introduced. Thereafter, the sheet waswashed with hot water of 60° C., followed by drying at 70° C. using ahot air dryer. Thus, a hydrophilic nonwoven sheet was obtained. On thehydrophilic nonwoven sheet thus obtained, the contact angle ofdechlorinated water was 0 degrees. FIG. 2 shows a 200×SEM micrograph ofa surface of the nonwoven sheet.

The hydrophilic nonwoven sheet was impregnated with water to 100 mass %with respect to the sheet by spraying. The sheet was subjected to gelprocessing using a pair of smooth rollers heated to 130° C. (a thermalroller) with a line pressure of 500 N/cm and a processing speed of 3.3m/min. Thus, an organic electrolyte battery separator of the presentinvention was obtained. In the thus-obtained separator, the averagefiber diameter of the pre-gel processing nonwoven sheet was 6.08 μm,while the average fiber diameter of fiber(s) other than theheat-and-humidity gelling resin was 7.22 μm. FIGS. 3A to 3D show 200×SEMmicrographs of a surface of the separator. In FIG. 3A, a portionextending downward from a right side of a middle thereof, which lookedlike a film, was a film-like gel material. Similarly, a portionextending over a vertical direction of a middle portion in FIG. 3B, aleft portion in FIG. 3C, and a left portion and an upper right portionin FIG. 3D were film-like gel materials. FIG. 4 shows a 500×SEMmicrograph of a cross-section of the battery separator.

Example 2

An organic electrolyte battery separator was obtained with a processsimilar to that of Example 1, except that the fiber 3 had 1.2 dtex(fiber diameter: 13.1 μm) and the fiber 4 had 1.2 dtex (fiber diameter:13.0 μm). The average fiber diameter of a pre-gel processing nonwovensheet of the resultant separator was 7.81 μm. The average fiber diameterof the fibers other than the heat-and-humidity gelling resin was 9.52μm.

Example 3

An organic electrolyte battery separator was obtained with a processsimilar to that of Example 1, except that the fiber 1 had 3.3 dtex(post-split minor axis thickness: 3.96 μm (PP), 4.06 μm (EVOH)). Theaverage fiber diameter of a pre-gel processing nonwoven sheet of theresultant separator was 6.78 μm. The average fiber diameter of thefibers other than the heat-and-humidity gelling resin was 7.68 μm.

Example 4

An organic electrolyte battery separator was obtained with a processsimilar to that of Example 1, except that the fiber 1 having a finenessof 1.4 dtex was changed to 70 mass % (post-split minor axis thickness:2.57 μm (PP), 2.66 μm (EVOH)) and the fiber 3 having 0.8 dtex waschanged to 30 mass % (fiber diameter: 10.3 μm). The average fiberdiameter of a pre-gel processing nonwoven sheet of the resultantseparator was 4.92 μm. The average fiber diameter of the fiber otherthan the heat-and-humidity gelling resin was 6.13 μm.

Example 5

50 mass % of the fiber 1 having a fineness of 1.2 dtex (post-split minoraxis thickness: 2.2 μm (PP), 2.28 μm (EVOH)), 30 mass % of the fiber 3having 0.8 dtex (fiber diameter: 10.3 μm), and 20 mass % of the fiber 4having 0.6 dtex (fiber diameter: 8.37 μm) were mixed to prepare awater-dispersed slurry to a concentration of 0.5 mass %. From thewater-dispersed slurry thus obtained, wetlaid webs having an mass perunit area of 12.5 g/m² was produced using a cylinder type wetpapermaking machine and a short wire type wet papermaking machine. Thetwo webs were combined together. Next, a thermal treatment was performedat 130° C. using a cylinder dryer, and at the same time, theheat-and-humidity gelling resin of the fiber 1 and the sheath componentof the fiber 4 temporarily bonded the fibers. The wetlaid nonwoven sheethaving an mass per unit area of 25 g/m² was rolled up. In the resultantwetlaid nonwoven sheet, substantially 100% of the fiber 1 was split andsubstantially uniformly dispersed in the nonwoven.

Next, the wetlaid nonwoven sheet was treated at room temperature (25°C.) for one minute in a processing chamber into which a gas mixtureconsisting of 1 volume % of fluorine, 73 volume % of oxygen, and 26volume % of nitrogen had been introduced. Thereafter, the sheet waswashed with ion-exchange water of 60° C., followed by drying at 70° C.using a hot air dryer. Thus, a hydrophilic nonwoven sheet was obtained.On the hydrophilic nonwoven sheet thus obtained, the contact angle ofdechlorinated water was 0 degrees.

The hydrophilic nonwoven sheet was impregnated with water to 100 mass %with respect to the sheet by spraying. The sheet was subjected to gelprocessing using a pair of plane rollers heated to 90° C. (a thermalroller) with a line pressure of 8000 N/cm and a processing speed of 7m/min. The sheet was subjected to thickness adjustment under the sameconditions as those described above. Thus, an organic electrolytebattery separator of the present invention was obtained. In thethus-obtained separator, the average fiber diameter of the pre-gelprocessing nonwoven sheet was 5.88 μm, while the average fiber diameterof the fibers other than the heat-and-humidity gelling resin was 7.09μm.

FIGS. 5A and 5B show 300×SEM micrographs of a surface of the nonwovensheet. FIGS. 5C and 5D show 300× cross-sectional photographs thereof.Also, FIGS. 6A and 6B show 300×SEM micrographs of a surface of theseparator. FIGS. 6C and 6D show 1000× cross-sectional photographsthereof.

Example 6

An organic electrolyte battery separator was obtained by a processsimilar to that of Example 5, except that 50 mass % of the fiber 1having a fineness of 1.2 dtex (post-split minor axis thickness: 2.2 μm(PP), 2.28 μm (EVOH)), 20 mass % of the fiber 3 having 0.8 dtex (fiberdiameter: 10.3 μm), 10 mass % of the fiber 4 having 0.6 dtex (fiberdiameter: 8.37 μm), and 20 mass % of a synthetic pulp were mixed. In thethus-obtained separator, the average fiber diameter (excluding thesynthetic pulp) of the pre-gel processing nonwoven sheet was 5.02 μm,while the average fiber diameter of the fibers (excluding the syntheticpulp) other than the heat-and-humidity gelling resin was 6.27 μm.

Comparative Example 1

An organic electrolyte battery separator was obtained by a processsimilar to that of Example 1, except that the separator was notimpregnated with water. In this case, the separator was shrunk duringthickness processing and was difficult to roll up.

Comparative Example 2

An organic electrolyte battery separator was obtained by a processsimilar to that of Example 1, except that the fiber 3 had 2.0 dtex(fiber diameter: 16.8 μm) and the fiber 4 had 2.0 dtex (fiber diameter:16.6 μm). In the thus-obtained separator, the average fiber diameter ofthe pre-gel processing nonwoven sheet was 9.66 μm, while the averagefiber diameter of the fibers other than the heat-and-humidity gellingresin was 11.99 μm.

Comparative Example 3

An organic electrolyte battery separator was obtained by a processsimilar to that of Example 1, except that the fiber 1 having a finenessof 1.4 dtex was changed to 20 mass % (post-split minor axis thickness:2.57 μm (PP), 2.66 μm (EVOH)), the fiber 3 having 0.8 dtex was changedto 50 mass % (fiber diameter: 10.3 μm), and the fiber 4 having 0.6 dtexwas changed to 30 mass % (fiber diameter: 8.37 μm). In the thus-obtainedseparator, the average fiber diameter of the pre-gel processing nonwovensheet was 8.51 μm, while the average fiber diameter of the fibers otherthan the heat-and-humidity gelling resin was 9.16 μm.

Comparative Example 4

An organic electrolyte battery separator was obtained by a processsimilar to that of Example 1, except that no hydrophilic treatment wasperformed before gel thickness processing. In this case, a contact angleof dechlorinated water was 105 degrees before gel processing, so thatmoisture was not uniformly permeated, resulting in non-uniform gelation.

Comparative Example 5

The fiber 1 was changed to the fiber 2 having a fineness of 1.4 dtex(post-split minor axis thickness: 2.57 μm (PP), 2.70 μm (HDPE)). Thermalroller processing was performed at 130° C. without giving moisture. Theresultant nonwoven was significantly shrunk during thickness processing,so that the sheet could not be rolled up.

Physical properties of the battery separators of Examples 1 to 6 andComparative Examples 1 to 5 are shown in Tables 1 to 3. TABLE 1 Example1 Example 2 Example 3 Example 4 fiber type fiber 1 fiber 1 fiber 1 fiber1 composite ratio (core/sheath) 50/50 50/50 50/50 50/50 fineness (dtex)1.4 1.4 3.3 1.4 post-split fineness (dtex) 0.088 0.088 0.206 0.088post-split minor axis thickness (μm) (PP)2.57 (PP)2.57 (PP)3.96 (PP)2.57(EVOH)2.66 (EVOH)2.66 (EVOH)4.06 (EVOH)2.66 content (mass %) 50 50 50 70fiber type fiber 3 fiber 3 fiber 3 fiber 3 fineness (dtex) 0.8 1.20 0.80.8 fiber diameter(μm) 10.3 13.1 10.3 10.3 content (mass %) 30 30 30 30fiber type fiber 4 fiber 4 fiber 4 fineness (dtex) 0.6 1.2 0.6 fiberdiameter(μm) 8.37 13 8.37 content (mass %) 20 20 20 fiber type content(mass %) heat-and-humidity gelling resin content (mass %) 25 25 25 35average fiber diameter (μm) 6.08 7.81 6.78 4.92 average fiber diameterof other fibers (μm) 7.22 9.52 7.68 6.13 pre-gel processing hydrophilictreatment Yes Yes Yes Yes moisture proportion (mass %) 100 100 100 100thermal roller temperature (° C.) 130 130 130 130 thermal roller linepressure (N/cm) 500 500 500 500 post-gel processing shrinkage ratio (%)1 3 0.5 1 mass per unit area (g/m²) 30 30 30 30 thickness (μm) 47 49 5343 specific volume(cm³/g) 1.56 1.63 1.77 1.43 pre-gel processing meanflow pore diameter (μm) 16.39 16.39 16.39 16.39 pre-gel processingbubble point pore diameter (μm) 26.61 26.61 26.61 26.61 post-gelprocessing mean flow pore diameter (μm) 1.69 3.89 2.56 1.38 post-gelprocessing bubble point pore diameter (μm) 7.38 16.3 12.01 6.91 meanflow pore diameter reduction rate (%) 89.7 77 84.4 91.6 puncturestrength (N) 6.79 6.01 6.2 5.72 standard deviation of puncture strength(N) 0.57 0.72 0.65 0.52 variation index of puncture strength 0.084 0.1200.105 0.091 contact angle of pre-hydrophilic treatment 105 105 105 105nonwoven sheet surface (degree) contact angle of pre-hydrophilictreatment and 0 0 0 0 pre-gel processing nonwoven sheet surface (degree)contact angle of post-gel processing separator 0 0 0 0 surface (degree)proportion of film-like gel material portion (%) 56 58 58 65

TABLE 2 Comparative Comparative Example 5 Example 6 Example 1 Example 2fiber type Fiber 1 fiber 1 fiber 1 fiber 1 composite ratio (core/sheath)50/50 50/50 50/50 50/50 fineness (dtex) 1.2 1.2 1.4 1.4 post-splitfineness (dtex) 0.075 0.075 0.088 0.088 post-split minor axis thickness(μm) (PP)2.20 (PP)2.20 (PP)2.57 (PP)2.57 (EVOH)2.28 (EVOH)2.28(EVOH)2.66 (EVOH)2.66 content (mass %) 50 50 50 50 fiber type Fiber 3fiber 3 fiber 3 fiber 3 fineness (dtex) 0.8 0.8 0.8 2 fiber diameter(μm) 10.3 10.3 10.3 16.8 content (mass %) 30 30 30 30 fiber type Fiber 4fiber 4 fiber 4 fiber 4 fineness (dtex) 0.6 0.6 0.5 2 fiber diameter(μm)8.37 8.37 8.37 16.6 content (mass %) 20 20 20 20 fiber type syntheticpulp content (mass %) 20 heat-and-humidity gelling resin content (mass%) 25 25 25 25 average fiber diameter (μm) 5.88 5.02 6.08 9.66 averagefiber diameter of other fibers (μm) 7.09 6.27 7.22 11.99 pre-gelprocessing hydrophilic treatment Yes Yes Yes Yes moisture proportion(mass %) 100 100 0 100 thermal roller temperature (° C.) 90 90 130 130thermal roll line pressure (N/cm) 8000 × 2 8000 × 2 500 500 times timespost-gel processing shrinkage ratio (%) 1 1 5 3 mass per unit area(g/m²) 25 20 30 30 thickness (μm) 35 30 47 58 specific volume(cm³/g) 1.41.5 1.57 1.93 pre-gel processing mean flow pore diameter (μm) 10.1511.44 16.39 16.39 pre-gel processing bubble point pore diameter (μm)20.19 21.06 26.61 26.61 post-gel processing mean flow pore diameter (μm)3.36 3.21 6.23 8.24 post-gel processing bubble point pore diameter (μm)12.94 9.15 21.2 21.1 mean flow pore diameter reduction rate (%) 66.971.9 62 49.7 puncture strength (N) 3.64 2.37 6.37 5.65 standarddeviation of puncture strength (N) 0.51 0.38 1.34 0.98 variation indexof puncture strength 0.140 0.160 0.210 0.173 contact angle ofpre-hydrophilic treatment 105 105 105 105 nonwoven sheet surface(degree) contact angle of pre-hydrophilic treatment and 0 0 0 0 pre-gelprocessing nonwoven sheet surface (degree) contact angle of post-gelprocessing separator 0 0 0 0 surface (degree) proportion of film-likegel material portion (%) 62 80 35 55

TABLE 3 Comparative Comparative Comparative Example 3 Example 4 Example5 fiber type fiber 1 fiber 1 fiber 2 composite ratio (core/sheath) 50/5050/50 50/50 fineness (dtex) 1.4 1.4 1.4 post-split fineness (dtex) 0.0880.088 0.088 post-split minor axis thickness (μm) (PP)2.57 (PP)2.57(PP)2.57 (EVOH)2.66 (EVOH)2.66 (PE)2.70 content (mass %) 20 50 50 fibertype fiber 3 fiber 3 fiber 3 fineness (dtex) 2 0.8 0.8 fiberdiameter(μm) 16.8 10.3 10.3 content (mass %) 50 30 30 fiber type fiber 4fiber 4 fiber 4 fineness (dtex) 2 0.5 0.5 fiber diameter(μm) 16.6 8.378.37 content (mass %) 20 20 20 fiber type content (mass %)heat-and-humidity gelling resin content (mass %) 10 25 0 average fiberdiameter(μm) 8.51 6.08 6.09 average fiber diameter of other fibers (μm)9.26 7.22 6.09 pre-gel processing hydrophilic treatment Yes No Yesmoisture proportion (%) 100 100 100 thermal roller temperature (° C.)130 130 130 thermal roll line pressure (N/cm) 500 500 500 post-gelprocessing shrinkage ratio (%) 5 5 8 mass per unit area (g/m²) 30 30 notthickness (μm) 46 47 measurable specific volume (cm³/g) 1.53 1.57pre-gel processing mean flow pore diameter(μm) 16.39 16.39 20.6 pre-gelprocessing bubble point pore diameter (μm) 26.61 26.61 46.2 post-gelprocessing mean flow pore diameter(μm) 7.76 3.89 not post-gel processingbubble point pore diameter (μm) 54.61 23.32 measurable mean flow porediameter reduction rate (%) 52.7 76.3 puncture strength (N) 6.02 6.37standard deviation of puncture strength (N) 0.98 1.33 variation index ofpuncture strength 0.163 0.209 contact angle of pre-hydrophilic treatment105 105 115 nonwoven sheet surface (degree) contact angle ofpre-hydrophilic treatment 40 no 50 and pre-gel processing nonwoven sheetsurface hydrophilic (degree) treatment contact angle of post-gelprocessing separator 45 105 no gel (degree) processing proportion offilm-like gel material portion (%) 33 57

As can be seen from Tables 1 to 3, it could be confirmed that in all ofExamples 1 to 6, a nonwoven was obtained that has a small pore diameter,an appropriate mean flow pore diameter range and bubble point porediameter range, and desired ranges of the standard deviation of thepuncture strength and the film degree of the gel material whilemaintaining a satisfactory level of gel processing ability. In aseparator comprising the nonwoven, the battery defect rate was low andno short circuits occurred. In Example 5, the thickness could bedecreased up to 35 μm by increasing the line pressure of the thermalroller to 8000 N/cm. In Example 6, by adding a synthetic pulp, thethickness could be further decreased to 30 μm, whereby the bubble pointpore diameter was also reduced to 10 μm or less.

On the other hand, in Comparative Example 1, the nonwoven was notimpregnated with water, so that the heat-and-humidity gelling resin didnot become a gel, and therefore, the pore diameter and thickness of theseparator could not be reduced. Further, since moisture was notprovided, the temperature of the thermal roller was applied directly tothe nonwoven. As a result, the temperature of the sheath resin of thefiber 3 was greater than or equal to the melting point, so that thenonwoven was shrunk significantly. When the nonwoven was used as aseparator, a fine powder short circuit occurred. In Comparative Example2, since the fiber diameter was large, a small pore diameter was notobtained. Therefore, when the nonwoven was used as a separator, a finepowder short circuit occurred. In Comparative Example 3, theheat-and-humidity gelling resin content was small, and therefore, theheat-and-humidity gelling resin was not sufficiently spread between thefibers. As a result, the pore diameter, particularly the bubble pointpore diameter, was not small. When such a nonwoven was used as aseparator, a fine powder short circuit occurred. In Comparative Example4, a hydrophilic treatment was not performed before gel thicknessprocessing, and therefore, the nonwoven could not be provided withmoisture uniformly, the bubble point pore diameter was not small andthere was a significant variation in the puncture strength. When thenonwoven was used as a separator, a fine powder short circuit occurred.In Comparative Example 5, since the heat-and-humidity gelling resin wasnot used, the nonwoven was significantly shrunk during thicknessprocessing, and therefore, was difficult to roll up.

Physical properties of the lithium ion secondary batteries of Example 1and Comparative Example 4 are shown in Table 4. TABLE 4 ComparativeExample 1 Example 4 short circuit characteristics ◯ X safety ◯ Xself-discharge Starting voltage (V) 3.7105 not amount voltage after 4hrs (V) 3.6241 measurable voltage difference (V) 0.0564 electric 0.5 Cdischarge 42.41 not capacity current 20 A   (100%) measurable output 1.0C discharge 42.11 characteristics current 40 A (99.29%) (Ah) 4.0 Cdischarge 41.02 current 80 A (96.72%) 6.0 C discharge 36.27 current 160A (85.52%)

Regarding the short circuit characteristics of a battery, when theresistance of the battery of Example 1 was measured using a megaelectrical resistance meter before injection of electrolytic solution,the meter displayed ∞, i.e., a short circuit was not observed. On theother hand, in Comparative Example 4, when the resistance was measured,the meter did not display ∞, i.e., a short circuit occurred.

Regarding the safety of a battery, in Example 1, as the charge amountwas increased, the cell voltage was linearly increased. When the batteryis overcharged to 155% of the electric capacity, decomposed gas wasgenerated from the bottom of the cell, but no other abnormality wasobserved. When the battery was further overcharged to 165%, generationof decomposed gas stopped and the test was ended. The battery heldsufficient electrolytic solution to function as a battery again andabnormal rupture did not occur. Thus, it was confirmed that the batterywas safely terminated. On the other hand, in Comparative Example 4,charge was continued before blockage occurred in the separator of thebattery, so that an internal pressure was increased to a limit of thebattery pack. Finally, gas and electrolytic solution suddenly burst andexploded.

Regarding the self-discharge amount and the electric capacity outputcharacteristics of the battery, Example 1 provided satisfactory values,i.e., excellent battery characteristics. On the other hand, inComparative Example 4, a short circuit occurred before producing thebattery, i.e., a battery could not be obtained.

INDUSTRIAL APPLICABILITY

The organic electrolyte battery separator of the present invention canbe preferably useful for an organic electrolyte battery, particularly alithium ion secondary battery. The organic electrolyte battery of thepresent invention can be used as a secondary battery for an ordinaryconsumer product, a hybrid electric vehicle (HEV) and a pure electricvehicle (PEV), and the like.

1-32. (canceled)
 33. An organic electrolyte battery separator, which iscomposed of a nonwoven comprising a heat-and-humidity gelling resincapable of gelling by heating in the presence of moisture and anotherfiber, the other fiber being fixed with a film gel material obtained bycausing the heat-and-humidity gelling resin to gel under heat andhumidity and be pressed and spread by pressing, and the nonwoven havinga mean flow pore diameter of 0.3 to 5 μm and a bubble point porediameter of 3 to 20 μm as measured in accordance with ASTM F 316
 86. 34.The organic electrolyte battery separator according to claim 33, whereinthe heat-and-humidity gelling resin is a heat-and-humidity gellingfiber, the heat-and-humidity gelling resin being provided at least at aportion of a surface of the heat-and-humidity gelling fiber.
 35. Theorganic electrolyte battery separator according to claim 33, wherein aproportion of the nonwoven occupied by the heat-and-humidity gellingresin is in a range of 10 to 50 mass %.
 36. The organic electrolytebattery separator according to claim 33, wherein the heat-and-humiditygelling resin is an ethylene-vinyl alcohol copolymer.
 37. The organicelectrolyte battery separator according to claim 33, wherein the otherfiber has a fiber diameter of 15 μm or less.
 38. The organic electrolytebattery separator according to claim 33, wherein an average fiberdiameter of the other fiber constituting the nonwoven is 10 μm or less.39. The organic electrolyte battery separator according to claim 33,wherein the fiber constituting the nonwoven composed theheat-and-humidity gelling resin and an olefin fiber.
 40. The organicelectrolyte battery separator according to claim 33, wherein the otherfiber includes a high-strength fiber having a single fiber strength of4.5 cN/dtex or more in a range of 5 to 250 parts by mass where theheat-and-humidity gelling resin is assumed to be 100 parts by mass. 41.The organic electrolyte battery separator according to claim 33, whereinthe other fiber includes a heat-melting fiber that does notsubstantially shrink at a temperature that causes the heat-and-humiditygelling resin to gel under heat and humidity to fix the other fiber, ina range of 10 to 300 parts by mass where the heat-and-humidity gellingresin is assumed to be 100 parts by mass.
 42. The organic electrolytebattery separator according to claim 33, wherein the nonwoven furthercomprises a synthetic pulp in addition to the other fiber.
 43. Theorganic electrolyte battery separator according to claim 33, wherein thesynthetic pulp is included in a range of 10 to 200 parts by mass wherethe heat-and-humidity gelling resin is assumed to be 100 parts by mass.44. The organic electrolyte battery separator according to claim 34,wherein an average fiber diameter of the heat-and-humidity gelling fiberand the other fiber is 10 μm or less.
 45. The organic electrolytebattery separator according to claim 34, wherein the heat-and-humiditygelling fiber has a fiber diameter of 1 to 6 μm.
 46. The organicelectrolyte battery separator according to claim 45, wherein theheat-and-humidity gelling fiber is a fiber provided by splitting asplittable composite fiber that contains the heat-and-humidity gellingresin and another resin, which are adjacent to each other in across-section of the fiber.
 47. The organic electrolyte batteryseparator according to claim 46, wherein, when the splittable compositefiber comprised of the heat-and-humidity gelling resin and anotherresin, which are adjacent to each other in a cross-section of the fiber,to be able to provide the heat-and-humidity gelling fiber, is assumed tobe 100 parts by mass, the nonwoven comprises, as the other fiber, ahigh-strength fiber having a single fiber strength of 4.5 cN/dtex ormore in a range of 10 to 200 parts by mass, and the nonwoven furthercomprises a heat-melting fiber that does not substantially shrink at atemperature that causes the heat-and-humidity gelling resin to gel underheat and humidity to fix the other fiber, in a range of 10 to 200 partsby mass.
 48. The organic electrolyte battery separator according toclaim 46, wherein, when the splittable composite fiber comprised of theheat-and-humidity gelling resin and another resin, which are adjacent toeach other in a cross-section of the fiber, to be able to provide theheat-and-humidity gelling fiber, is assumed to be 100 parts by mass, thenonwoven comprises, as the other fiber, a high-strength fiber having asingle fiber strength of 4.5 cN/dtex or more in a range of 6.25 to 120parts by mass, the nonwoven further comprises a heat-melting fiber thatdoes not substantially shrink at a temperature that causes theheat-and-humidity gelling resin to gel under heat and humidity to fixthe other fiber, in a range of 12.5 to 120 parts by mass, and thenonwoven further comprises the synthetic pulp in a range of 6.25 to 120parts by mass.
 49. The organic electrolyte battery separator accordingto claim 34, wherein the fiber constituting the nonwoven is a shortfiber having a fiber length in a range of 1 mm to 20 mm, and thenonwoven is a wetlaid nonwoven obtained by a wetlaying process using theshort fiber.
 50. The organic electrolyte battery separator according toclaim 49, wherein the splittable composite fiber is split during thewetlaying step to provide a heat-and-humidity gelling fiber, and theheat-and-humidity gelling fiber is substantially uniformly present inthe nonwoven.
 51. The organic electrolyte battery separator according toclaim 33, wherein a surface of the nonwoven is partially covered with afilm gel material.
 52. The organic electrolyte battery separatoraccording to claim 51, wherein an area proportion of the film gelmaterial with respect to an entire surface of the nonwoven is in a rangeof 40% to 90%.
 53. The organic electrolyte battery separator accordingto claim 33, wherein a contact angle of dechlorinated water dropped on asurface of the nonwoven is 60 degrees or less 5 seconds after droppingof the dechlorinated water.
 54. The organic electrolyte batteryseparator according to claim 33, wherein the nonwoven has a puncturestrength of 2 N or more and a standard deviation of 1.1 N or less. 55.The organic electrolyte battery separator according to claim 54, whereina variation index of the puncture strength of the nonwoven is 0.165 orless, the variation being calculated from the puncture strength and thestandard deviation using the following expression:variation index of puncture strength=standard deviation/puncturestrength.
 56. The organic electrolyte battery separator according toclaim 33, wherein the separator has a thickness in a range of 15 μm to80 μm and the nonwoven has a specific volume in a range of 1.2 cm³/g to2.5 cm³/g.
 57. A method for producing an organic electrolyte batteryseparator, which is composed of a nonwoven comprising aheat-and-humidity gelling fiber in which a resin capable of gelling byheating in the presence of moisture is present on at least a portion ofa surface of the fiber, and another fiber, the method comprising atleast all of the following steps A to D of: A. preparing a nonwovensheet comprising the heat-and-humidity gelling fiber and the otherfiber; B. subjecting the nonwoven sheet to a hydrophilic treatment; C.providing moisture to the hydrophilic-treated nonwoven sheet to obtain awater-containing sheet; and D. subjecting the water-containing sheet togel processing by pressing and a heat-and-humidity treatment using aheat treatment device that is set to a certain temperature within arange of no less than a temperature at which the heat-and-humiditygelling resin gels and no more than “the melting point of theheat-and-humidity gelling resin −20° C.”, to cause the heat-and-humiditygelling resin to gel and be pressed and spread to form a film, andfixing the other fiber using the heat-and-humidity gelling resin gel.58. The organic electrolyte battery separator producing method accordingto claim 57, wherein the average fiber diameter of the nonwoven sheet is10 μm or less.
 59. The organic electrolyte battery separator producingmethod according to claim 57, wherein a proportion of the moistureprovided to the hydrophilic-treated nonwoven sheet is in a range of 20mass % to 300 mass %.
 60. The organic electrolyte battery separatorproducing method according to claim 57, wherein a contact angle ofdechlorinated water dropped on a surface of the hydrophilic-treatednonwoven sheet is 60 degrees or less 5 seconds after dropping of thedechlorinated water
 61. The organic electrolyte battery separatorproducing method according to claim 57, wherein the hydrophilictreatment is an exposure to fluorine gas atmosphere.
 62. The organicelectrolyte battery separator producing method according to claim 57,wherein the gel processing is press processing using a thermal roller,and a line pressure of the thermal roller is in a range of 350 N/cm to10000 N/cm.
 63. An organic electrolyte battery comprising the separatoraccording to claim 33.